The Starbase four element ‘orthoscopic’ series of eyepieces are distributed by Takahashi Seisakusho Ltd. There are supposedly five in the range consisting of: 20mm, 18mm, 14mm, 9mm and 6mm focal lengths. The 6mm and 14mm versions are bundled with the Starbase 80 telescope package.
The Starbase achromat and the eyepiece series are apparently both made by the Kubota Optical Corporation in Hanamaki, Japan. The eyepieces are not a traditional Abbe orthoscopic design and are purportedly an asymmetrical doublet defined and designated as an Orthoscopic Plossl (Orthoscopic/PL). They are recommended for use with focal ratios up to
“In the early days, it was made by Cook in England and Steinheil in Germany. This is an achromat type eyepiece that combines two Ramsden lenses. A well-made Japanese-made eyepiece is an almighty eyepiece that can be used from low to high magnification because ghosts are not noticeable and spherical aberration and distortion are small. By the way, NIKON's orthoscopic eyepieces, which are still very popular today, were PL type”
~ op cit (diagram and definition from the Scopetech webpage).
Etymologically the compound adjective ‘orthoscopic’ literally means corrected vision. Unlike most contemporary modern eyepieces the Starbase series probably aren’t edge-blacked. They feature a ‘retro’ volcano top without rubber eyeguards. The eyepieces each have a single high quality coating as opposed to being multi-coated (I'll return to this later). Kubota proclaim that the rationale behind using only a single coating of superior quality is that it gives much better transmission than relatively inexpensive mass produced multi-coatings. Although it has also been posited that it is more to do with axial light scatter. Except for the barrel undercut they have the vintage appearance of an erstwhile era. The
The 20mm has a 45°
It should be enough when placed in a 1.25” diagonal. I would have concerns about it coming loose in a 2” diagonal or a Newtonian focuser. My Baader filters had no problems in any of the four eyepieces. Interestingly the
At 53° the 14mm has the widest
The 9mm has a 45° field and the 7mm eye relief is about average for its focal length. By comparison my 9mm Circle-T Abbe has a 7.6mm eye relief. When used in conjunction with the Vixen Barlow in my 72ED DS Pro the 9mm Orthoscopic/PL really came into its own as a planetary eyepiece. The Barlow slightly improved the close eye relief. Both Saturn and Jupiter were very sharp at 93.3x. Colour separation and contrast were excellent. The Cassini Division and some surface detail on Saturn were easily observed as was Titan. I was impressed with the amount of detail I could actually see as Jupiter approached transit. Although occasionally I thought I detected a tiny bit of scatter. The planet was quite bright and only a few weeks from opposition though. I was also using a Baader Neodymium filter in the diagonal nosepiece which may have contributed to this effect in some way. It was a damp and dew laden early morning session. With excessive humidity filters can often have a tendency to fog slightly in the nosepiece. I believe I also occasionally saw a hint of the reflection of my own cornea, which may be a consequence of the single coating. After some use this disappeared. In later sessions I didn’t notice either phenomena. The barrel undercut plays well in the Vixen Barlow as it has no compression ring.
With only 4mm of eye relief and a 43° apparent field the 6mm Orthoscopic/PL is the least ergonomic of the quartet. Again, compared to an Abbe of the same focal length, it has almost a millimetre less eye relief. Images of Saturn and Jupiter used without a Barlow in the 72ED at 70x were very sharp and bright. The intensity of the rich colours and excellent contrast impressed me. I was immediately quite taken with the 6mm O/PL, especially when used in the Vixen Barlow. The volcano top almost certainly contributed to the comparative ease of viewing and eye positioning. I’d expected it to be more demanding to use, so this was a pleasant surprise. At 140x (with the Barlow) the 6mm O/PL gave an approximate 0.5mm exit pupil. I split ε Boötis and I thought it was one of the best views of the binary I’d had so far that year. As Cassiopeia got higher in the sky I discovered ι Cassiopeiae also split beautifully. I’m convinced these views were enhanced by the above average transmission of the single coating.
Saturn still looked excellent even when it was past transit. During the first session it wasn’t quite as sharp on Jupiter at 140x. This wasn’t surprising however as the seeing was only average and the transparency was relatively poor. What was surprising was just how well the 6mm performed on Jupiter at 140x in a 72mm ED doublet. In a later session of better conditions I could see what appeared like Ganymede’s shadow on the surface near the limb. I actually first witnessed this at 93x with the Barlowed 9mm. I knew Ganymede would eventually become visible as it transited the surface. I impatiently switched back to the 6mm as I wanted to view this emergence before I lost the transparency. Eventually I was rewarded with the bright point of light of Ganymede seemingly separating itself from the planetary limb.
The Starbase O/PL’s were originally acquired for my 102mm Sky-Watcher SkyMax Maksutov Cassegrain. Its focal ratio of
The 20mm Starbase gave me a nice view of Saturn and Jupiter at 65x. It was when I started using the 14mm it started getting interesting. Although I did notice the undercut snagging occasionally when swapping eyepieces. The three screws of the Baader helical compression ring can often be a little finicky with barrel undercuts. The 14mm O/PL gave a fairly sharp 92.8x. The seeing was above average, but not as good as the previous night. Jupiter’s
Overall I like these 'retro' eyepieces. Although purists may find they perform better at
So most things that are "love it or hate it" turn out to be at least mildly pleasurable. I think that the minimalist design and simple coatings helps with light throughput. I can't find the planetary comparison of the KKs and Starbase but with brighter targets the KKs were crisper.
